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- #include <bits/stdc++.h>
- using namespace std;
- // Merges two subarrays of arr[].
- // First subarray is arr[l..m]
- // Second subarray is arr[m+1..r]
- void merge(int arr[], int l, int m, int r, int* count_crossline)
- {
- int i, j, k;
- int n1 = m - l + 1;
- int n2 = r - m;
- /* create temp arrays */
- int L[n1], R[n2];
- /* Copy data to temp arrays L[] and R[] */
- for (i = 0; i < n1; i++)
- L[i] = arr[l + i];
- for (j = 0; j < n2; j++)
- R[j] = arr[m + 1 + j];
- /* Merge the temp arrays back into arr[l..r]*/
- i = 0; // Initial index of first subarray
- j = 0; // Initial index of second subarray
- k = l; // Initial index of merged subarray
- while (i < n1 && j < n2) {
- if (L[i] <= R[j]) {
- arr[k] = L[i];
- i++;
- }
- else {
- arr[k] = R[j];
- //====================================//
- //======= MAIN PORTION OF CODE ======//
- //===================================//
- // add all line which is cross by current element
- *count_crossline += (n1 - i);
- j++;
- }
- k++;
- }
- /* Copy the remaining elements of L[], if there
- are any */
- while (i < n1) {
- arr[k] = L[i];
- i++;
- k++;
- }
- /* Copy the remaining elements of R[], if there
- are any */
- while (j < n2) {
- arr[k] = R[j];
- j++;
- k++;
- }
- }
- /* l is for left index and r is right index of the
- sub-array of arr to be sorted */
- void mergeSort(int arr[], int l, int r, int* count_crossline)
- {
- if (l < r) {
- // Same as (l+r)/2, but avoids overflow for
- // large l and h
- int m = l + (r - l) / 2;
- // Sort first and second halves
- mergeSort(arr, l, m, count_crossline);
- mergeSort(arr, m + 1, r, count_crossline);
- merge(arr, l, m, r, count_crossline);
- }
- }
- // function return count of cross line in an array
- int countCrossLine(int arr[], int n)
- {
- int count_crossline = 0;
- mergeSort(arr, 0, n - 1, &count_crossline);
- return count_crossline;
- }
- // driver program to test above function
- int main()
- {
- int q;
- cin >> q;
- int n;
- int *arr;
- for (int i = 0; i < q; i++)
- {
- cin >> n;
- arr = new int[n];
- for (int j = 0; j < n; j++)
- {
- cin >> arr[j];
- }
- cout << countCrossLine(arr, n) << endl;
- }
- return 0;
- }
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